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United States Patent |
5,683,845
|
Sata
,   et al.
|
November 4, 1997
|
Positively chargeable toner for nonmagnetic one-component developing
method
Abstract
The positively chargeable toner used for a nonmagnetic one-component
developing method includes a toner particle and fine
polytetrafluoroethylene particles, the toner particle having (a) a binder
resin having a polyester resin having an acid value of 10 mg KOH/g or
less; (b) a colorant; and (c) a charge control agent, and the fine
polytetrafluoroethylene particles, whose average primary particle size is
at least 0.05 .mu.m and less than 0.5 .mu.m, being externally added to the
surface of the toner particle. The nonmagnetic one-component developing
method includes the step of loading the above positively chargeable toner
in a developer device for a nonmagnetic one-component toner.
Inventors:
|
Sata; Shin-ichi (Wakayama, JP);
Shimizu; Jun (Wakayama, JP);
Maruta; Masayuki (Wakayama, JP)
|
Assignee:
|
KAO Corporation (Tokyo, JP)
|
Appl. No.:
|
744818 |
Filed:
|
November 6, 1996 |
Foreign Application Priority Data
Current U.S. Class: |
430/109.4; 430/108.11; 430/903 |
Intern'l Class: |
G03G 009/097 |
Field of Search: |
430/110,109,106
|
References Cited
U.S. Patent Documents
4175167 | Nov., 1979 | van Lier | 429/59.
|
4804622 | Feb., 1989 | Tanaka et al. | 430/107.
|
Other References
JP-A-62-195676 (English Abstract only).
JP-A-62-195677 (English Abstract only).
JP-A-62-195678 (English Abstract only).
JP-A-62-195679 (English Abstract only).
JP-A-62-195680 (English Abstract only).
|
Primary Examiner: Goodrow; John
Attorney, Agent or Firm: Birch, Stewart, Kolasch & Birch, LLP
Claims
What is claimed is:
1. A positively chargeable toner used for a nonmagnetic one-component
developing method, comprising a toner particle and fine
polytetrafluoroethylene particles, said toner particle comprising:
(a) a binder resin comprising a polyester resin having an acid value of 10
mg KOH/g or less;
(b) a colorant; and
(c) a charge control agent, and said fine polytetrafluoroethylene
particles, whose average primary particle size is at least 0.05 .mu.m and
less than 0.5 .mu.m, being adhered to the surface of said toner particle.
2. The positively chargeable toner according to claim 1, wherein said
polyester resin is obtainable by carrying out condensation polymerization
of a polycarboxylic acid component other than aromatic polycarboxylic
acids and a polyhydric alcohol component.
3. The positively chargeable toner according to claim 1, wherein said fine
polytetrafluoroethylene particles are externally added in an amount of
from 0.01 to 1.5 parts by weight, based on 100 parts by weight of said
toner particle.
4. The positively chargeable toner according to claim 2, wherein said
polycarboxylic acid component is one or more compounds selected from the
group consisting of maleic acid, fumaric acid, citraconic acid, iraconic
acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid,
cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid,
azelaic acid, malonic acid, n-butylsuccinic acid, n-butenylsuccinic acid,
isobutylsuccinic acid, isobutenylsuccinic acid, n-octylsuccinic acid,
n-octenylsuccinic acid, isooctylsuccinic acid, isooctenylsuccinic acid,
n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid,
isododecenyl-succinic acid, acid anhydrides thereof, and lower alkyl
esters thereof.
5. The positively chargeable toner according to claim 2, wherein said
polycarboxylic acid component is one or more compounds selected from the
group consisting of 1,2,4-benzenetricarboxylic acid,
2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid,
1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid,
1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane,
1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane,
1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, Empol trimer acid,
acid anhydrides thereof, lower alkyl esters thereof.
6. The positively chargeable toner according to claim 2, wherein said
polycarboxylic acid component is a tetracarboxylic acid having the
following general formula (II):
##STR4##
wherein X stands for an alkylene group or an alkenylene group, each having
from 5 to 30 carbon atoms and having one or more side chains each with 3
carbon atoms or more.
7. The positively chargeable toner according to claim 2, wherein said
polyhydric alcohol component comprises a diol component represented by the
following general formula (I):
##STR5##
wherein R stands for an ethylene group or a propylene group; and x and y
independently stand for integers of 1 or more, wherein an average sum of x
and y is from 2 to 7.
8. The positively chargeable toner according to claim 1, wherein said
charge control agent is added in an amount of 0.1 to 8.0 parts by weight,
based on 100 parts by weight of the binder resin.
9. The positively chargeable toner according to claim 1, wherein the
positively chargeable toner is employed in a nonmagnetic one-component
developing method using a positively charged organic photoconductor.
10. A nonmagnetic one-component developing method comprising the step of
loading the positively chargeable toner according to claim 1 in a
developer device for a nonmagnetic one-component toner.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positively chargeable toner used for
development of electrostatic latent images in electrophotography,
electrostatic printing, and electrostatic recordings, particularly used
for development of electrostatic latent images formed by nonmagnetic
one-component development.
2. Discussion of the Related Art
Conventionally, developing methods utilizing such methods as
electrophotography include two-component developing methods using a
developer comprising a magnetic carrier and a toner, and one-component
developing methods containing no magnetic carrier. The one-component
developing methods can be further classified into magnetic one-component
developing methods and nonmagnetic one-component developing methods
depending upon whether or not a magnetic material is contained in the
toner.
Among the above developing methods, two-component magnetic brush developing
methods using a developer consisting of two components, namely, a toner
and a carrier, have been mainly used conventionally, the carrier being
used for the purposes of supplying electric charges to the toner and of
conveying the charged toner onto the electrostatic latent image portion by
a magnetic force. However, in the two-component magnetic brush developing
method, since a magnetic force is utilized in the conveying of the
developer, a magnet has to be placed in the inner portion of the developer
roller, and the carrier is made of a metal or an oxide thereof such as
iron powder and ferrite. Therefore, the developer device and the developer
become undesirably heavy, thereby making it difficult to miniaturize and
thus reduce the weight of the overall recording device.
Also, as disclosed in U.S. Pat. Nos. 3,909,258 and 4,121,931, there have
been conventionally well used magnetic one-component developing methods
comprising the step of conveying a toner to the electrostatic latent image
portion without using a carrier, the methods being carried out by
utilizing a magnetic force owned by the toner containing a magnetic
material therein. However, a magnet has to be also placed in the inner
portion of the developer roller in this developing method, making it
disadvantageous from the aspect of weight reduction of the developer
device. Also, since the magnetic material is contained in the inner
portion of the toner, it is practically impossible to be used as color
toners.
In order to solve the problems in these developing methods, much studies
have been recently conducted on nonmagnetic one-component developing
methods wherein a toner alone is used without containing any magnetic
powder, as disclosed, for instance, in U.S. Pat. Nos. 2,895,847 and
3,152,012, and Japanese Patent Examined Publication Nos. 41-9475, 45-2877,
and 54-3624.
On the other hand, the photoconductors which are used in the above
developing methods include organic and inorganic photoconductors, which
are further classified into positively charged ones and negatively charged
ones depending upon its polarity. Among them, the organic photoconductors
have been widely used as photoconductors for copy machines and printers
because of their superior properties in productivity, environmental
stability, and machinability, as compared to those of the inorganic
photoconductors.
However, in the function-separation type organic photoconductors which have
been in practical use so far, since hole transport materials are used in
CTL, these organic photoconductors have been negatively charged types.
Therefore, a large amount of ozone is generated by negative corona
discharge, thereby causing such problems as requiring equipments for ozone
treatment apparatus and deteriorating the surface of the photoconductor
drum. In view of these problems, the development for positively charged
organic photoconductors has been made, some of which are presently in
practical use.
However, since the positively charged organic photoconductors have low
sensitivity when compared with the conventionally used inorganic
photoconductors, such as selenium-based photoconductors, the following
problems newly arise in the design of the toner used. In other words, the
term "the sensitivity of the photoconductor is low" means that in a case
of a reverse development, for instance, even higher development bias
voltage has to be applied for obtaining the same image density, which
results in a smaller potential difference between the surface voltage of
the unexposed portion and the developing bias voltage than that of the
inorganic photoconductor, thereby generating much background. Further,
since the organic photoconductors have poorer surface strength than that
of the inorganic photoconductors, the durability of the organic
photoconductor is low. Therefore, it has been necessary to make the life
of the organic photoconductor longer.
On the other hand, as for binder resin for toners, various resins,
including styrenic copolymers, such as polystyrenes, styrene-butadiene
copolymers, and styrene-acrylic copolymers; ethylenic copolymers, such as
polyethylenes and ethylene-vinyl acetate copolymers; poly(meth)acrylic
acid esters; polyester resins; epoxy resins; and polyamide resins, have
been used. Among these resins, the polyester resins are particularly used
as resins for toners having excellent low-temperature fixing ability.
Also, the polyester resins inherently have good resin toughness, so that
the durability of the resin can be improved while retaining the
low-temperature fixing ability, and thus making them suitable for
nonmagnetic one-component toner wherein a stress is more liable to be
exerted on a toner by a charging blade.
An object of the present invention is to provide a positively chargeable
toner used for a nonmagnetic one-component developing method.
Another object of the present invention is to provide a nonmagnetic
one-component developing method using the above positively chargeable
toner.
These and other objects of the present invention will be apparent from the
following description.
SUMMARY OF THE INVENTION
As a result of intensive research in view of the above problems, the
present inventors have found that the above problems can be solved by
using a positively chargeable toner used for a nonmagnetic one-component
developing method, comprising fine polytetrafluoroethylene particles
having a particular particle size and a toner particle comprising a
polyester resin having an acid value of 10 mg KOH/g or less as a binder
resin, the fine polytetrafluoroethylene particles being externally added
to the surface of the toner particle. The present invention has been
completed based upon these findings.
In one aspect, the present invention is concerned with a positively
chargeable toner used for a nonmagnetic one-component developing method,
comprising a toner particle and fine polytetrafluoroethylene particles,
the toner particle comprising:
(a) a binder resin comprising a polyester resin having an acid value of 10
mg KOH/g or less;
(b) a colorant; and
(c) a charge control agent, and the fine polytetrafluoroethylene particles,
whose average primary particle size is at least 0.05 .mu.m and less than
0.5 .mu.m, being externally added to the surface of the toner particle.
In another aspect, the present invention is concerned with a nonmagnetic
one-component developing method comprising the step of loading the above
positively chargeable toner in a developer device for a nonmagnetic
one-component toner.
DETAILED DESCRIPTION OF THE INVENTION
The positively chargeable toner used for a nonmagnetic one-component
developing method, comprises a toner particle and fine
polytetrafluoroethylene particles, the toner particle comprising:
(a) a binder resin comprising a polyester resin having an acid value of 10
mg KOH/g or less;
(b) a colorant; and
(c) a charge control agent, and the fine polytetrafluoroethylene particles
whose average primary particle size is at least 0.05 .mu.m and less than
0.5 .mu.m being externally added to the surface of the toner particle.
The average primary particle size of the fine polytetrafluoroethylene
particles is 0.05 .mu.m or more and less than 0.5 .mu.m, preferably from
0.1 to 0.45 .mu.m, more preferably from 0.15 to 0.4 .mu.m. When the
average primary particle size of the fine polytetrafluoroethylene
particles is 0.05 or more, the fine polytetrafluoroethylene particles
being externally added to the surface of the toner particle are not likely
to be embedded in the toner particle during continuous printing, thereby
maintaining the advantageous effects of the present invention. On the
other hand, when the average primary particle size is less than 0.5, the
fine polytetrafluoroethylene particles are not easily detached from the
toners, thereby making it possible to achieved the effects of the present
invention. Here, the average primary particle size of the fine
polytetrafluoroethylene particles is obtained by calculating a
number-average of the primary particle size obtained by taking
measurements from an electron micrograph.
More specifically, the fine polytetrafluoroethylene particles used herein
include those having nearly spherical shapes produced by emulsification
polymerization. Examples thereof may be those which are commercially
available, including "KTL-500F" (manufactured by Kitamura, whose average
primary particle size is 0.3 .mu.m); "LUBRON L2" (manufactured by Daikin
Industries, Ltd., whose average primary particle size is 0.3 .mu.m);
LUBRON L5" (manufactured by Daikin Industries, Ltd., whose average primary
particle size is 0.2 .mu.m); "FLUON LUBRICANT L170J" (manufactured by
Asahi ICI Fluoropolymers, whose average primary particle size is 0.1
.mu.m); "FLUON LUBRICANT L172J" (manufactured by Asahi ICI Fluoropolymers,
whose average primary particle size is 0.1 .mu.m); "MP-1100" (manufactured
by Mitsui-Dupont Fluorochemicals, whose average primary particle size is
0.2 .mu.m); "MP-1200" (manufactured by Mitsui-Dupont Fluorochemicals,
whose average primary particle size is 0.3 .mu.m); and "TLP-10F-l"
(manufactured by Mitsui-Dupont Fluorochemicals, whose average primary
particle size is 0.2 .mu.m).
The amount of the fine polytetrafluoroethylene particles is preferably from
0.01 to 1.5 parts by weight, more preferably from 0.05 to 1.0 part by
weight, based on 100 parts by weight of the toner particle. The amount of
the fine polytetrafluoroethylene particles is preferably from 0.1 to 1.5
parts by weight or less from the viewpoint of having good flowability and
conveyability of the toners, thereby maintaining good image density, and
also making it possible to prevent background on the formed images and
background on the photoconductors.
In the present invention, the fine polytetrafluoroethylene particles are
used for the following reasons. The fine polytetrafluoroethylene particles
themselves have a larger negative chargeability by triboelectric charging
when compared with other fluororesins, such as poly(vinylidene fluoride)
plastics, so that good triboelectric charging of the resulting toner can
be achieved during blending before passing the toners through the charging
blade or while passing the toners through the charging blade. Also, since
the melting point of the polytetrafluoroethylene is high and the
coefficient of friction is low, the abrasion of the photoconductor at the
cleaning portion can be notably reduced, so that the toners are not liable
to be melt-fused to the photoconductor, thereby making the life of the
photoconductor longer.
The methods for externally adding the above fine polytetrafluoroethylene
particles to the surface of the toner particle are not particularly
limited as long as they allow to adhere the fine polytetrafluoroethylene
particles to the surface of the toner particle, and any of known methods
may be employed, including those blending methods using Henschel mixers,
microspeed mixers, and super mixers.
The positively chargeable toners of the present invention comprises a
binder resin, a colorant, and a charge control agent, which may optionally
comprise offset inhibitors and other additives.
The binder resins usable in the present invention are polyester resins
having an acid value of 10 mg KOH/g or less, preferably those having an
acid value of from 0 to 6 mg KOH/g. The acid value is preferably 10 mg
KOH/g or less from the viewpoint of alleviating the negative chargeability
of the resin itself, so that the resin can be suitably used for a
positively chargeable toner of the present invention.
The acid value of the polyester resins may be controlled to a level of 10
mg KOH/g or less by such a method comprising adjusting the ratio between
alcohol components and carboxylic acid components during the polyester
production in a system rich in alcohol components, or a method comprising
carrying out the condensation reaction until all of the carboxylic acids
are polymerized.
The polyester resins can be obtained by the condensation polymerization of
polyhydric alcohol components and polycarboxylic acid components, namely
the condensation polymerization between a polyhydric alcohol and a
polycarboxylic acid, a polycarboxylic acid anhydride or a polycarboxylic
ester.
Among the alcohol components, the diol components may be those represented
by the following general formula (I):
##STR1##
wherein R stands for an ethylene group or a propylene group;. and x and y
independently stand for integers of 1 or more, wherein an average sum of x
and y is from 2 to 7.
Examples thereof include
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane,
polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane,
polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane,
polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane
, and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane.
In addition, in certain cases, ethylene glycol, diethylene glycol,
triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,
1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol,
1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol,
polyethylene glycol, polypropylene glycol, polytetramethylene glycol,
bisphenol A, hydrogenated bisphenol A, propylene adducts of bisphenol A,
ethylene adducts of bisphenol A, and other dihydric alcohols may be also
added.
Examples of the trihydric or higher polyhydric alcohols include sorbitol,
1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol,
tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol,
2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane,
trimethylolpropane, 1,3,5-trihydroxymethylbenzene, and other trihydric or
higher polyhydric alcohols.
Among these alcohols, polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane
and polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane are preferably
used.
In the present invention, these dihydric alcohol monomers and trihydric or
higher polyhydric alcohol monomers may be used singly or in combination.
The polycarboxylic acids, the polycarboxylic acid anhydrides, and the
polycarboxylic esters, include the following.
As for the acid components, examples of the dicarboxylic acid components
include maleic acid, fumaric acid, citraconic acid, iraconic acid,
glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid,
cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid,
azelaic acid, and malonic acid; and alkylsuccinic or alkenylsuccinic
acids, such as n-butylsuccinic acid, n-butenylsuccinic acid,
isobutylsuccinic acid, isobutenylsuccinic acid, n-octylsuccinic acid,
n-octenylsuccinic acid, isooctylsuccinic acid, isooctenylsuccinic acid,
n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid,
and isododecenyl-succinic acid. Also, acid anhydrides of these
dicarboxylic acids, lower alkyl esters thereof, and other dicarboxylic
acid components are also included.
Examples of the tricarboxylic or higher polycarboxylic acid components
include 1,2,4-benzenetricarboxylic acid (trimellitic acid),
2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid,
1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid,
1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane,
1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane,
1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, Empol trimer acid,
acid anhydrides thereof, lower alkyl esters thereof, and other
tricarboxylic or higher polycarboxylic acid components.
In the present invention, these dicarboxylic acid monomers and trihydric or
higher polycarboxylic acid monomers may be used singly or in combination.
In addition, examples of polycarboxylic acids include a tetracarboxylic
acid having the following general formula (II):
##STR2##
wherein X stands for an alkylene group or an alkenylene group, each having
from 5 to 30 carbon atoms and having one or more side chains each with 3
or more carbon atoms.
Examples thereof include the following items (1) to (12):
(1) 4-Neopentylidenyl-1,2,6,7-heptanetetracarboxylic acid;
(2) 4-Neopentyl-1,2,6,7-heptene(4)-tetracarboxylic acid;
(3) 3-Methyl-4-heptenyl-1,2,5,6-hexanetetracarboxylic acid;
(4) 3-Methyl-3-heptyl-5-methyl-1,2,6,7-heptene(4)-tetracarboxylic acid;
(5) 3-Nonyl-4-methyldenyl-1,2,5,6-hexanetetracarboxylic acid;
(6) 3-Decylidenyl-1,2,5,6-hexanetetracarboxylic acid;
(7) 3-Nonyl-1,2,6,7-heptene(4)-tetracarboxylic acid;
(8) 3-Decenyl-1,2,5,6-hexanetetracarboxylic acid;
(9) 3-Butyl-3-ethylenyl-1,2,5,6-hexanetetracarboxylic acid;
(10) 3-Methyl-4-butylidenyl-1,2,6,7-heptanetetracarboxylic acid;
(11) 3-Methyl-4-butyl-1,2,6,7-heptene(4)-tetracarboxylic acid; and
(12) 3-Methyl-5-octyl-1,2,6,7-heptene(4)-tetracarboxylic acid.
The polyester resins in the present invention are obtainable by carrying
out condensation polymerization of the above polyhydric alcohol components
and the polycarboxylic acid components. For instance, the condensation
polymerization may be carried out at a temperature of from 180 to
250.degree. C. in an inert gas atmosphere. In order to accelerate the
above reaction, conventionally used esterification catalysts, such as zinc
oxide, tin (II) oxide, dibutyltin oxide, and dibutyltin dilaurate, may be
used. To achieve the same purpose, the polyester resins may be prepared
under a reduced pressure.
Examples of the polyester resins produced by the methods described above
are those having an acid value of 10 mg KOH/g or less, of the polyesters
disclosed in Japanese Patent Laid-Open Nos. 62-195676, 62-195677,
62-195678, 62-195679, and 62-195680.
Among them, the polyesters obtainable by condensation polymerization of
polycarboxylic acid components other than aromatic polycarboxylic acid
components and polyhydric alcohols are preferably used as the binder
resins of the present invention. This is because the acid strength of the
polycarboxylic acid components other than the aromatic polycarboxylic acid
components is lower and its pKa, wherein Ka is a dissociation constant, is
smaller than those of the aromatic polycarboxylic acids.
Among the polycarboxylic acid components listed above, examples of the
polycarboxylic acid components other than aromatic polycarboxylic acid
components include dicarboxylic acids, such as maleic acid, fumaric acid,
and alkylsuccinic and alkenylsuccinic acids; tricarboxylic acids, such as
trimellitic acid, 1,2,4-butanetricarboxylic acid and
1,2,5-hexanetricarboxylic acid; and tetracarboxylic acids, such as
1,2,7,8-octanetetracarboxylic acid and tetracarboxylic acids having the
general formula (II), acid anhydrides thereof, and lower alkyl esters
thereof whose alkyl moieties have 1 to 4 carbon atoms.
Among them, in particular, trimellitic acid or a derivative thereof is
preferably used because it is inexpensive and the reaction control is
easy.
Examples of the colorants used in the present invention include carbon
black; inorganic pigments, such as iron black; acetoacetic arylamide-based
monoazo yellow pigments, such as C.I. Pigment Yellow 1, C.I. Pigment
Yellow 3, C.I. Pigment Yellow 74, C.I. Pigment Yellow 97, and C.I. Pigment
Yellow 98; acetoacetic arylamide-based bisazo yellow pigments, such as
C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14,
and C.I Pigment Yellow 17; yellow dyes, such as C.I. Solvent Yellow 19,
C.I. Solvent Yellow 77, C.I. Solvent Yellow 79, and C.I. Disperse Yellow
164; red or crimson pigments, such as C.I. Pigment Red 48, C.I. Pigment
Red 49:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57, C.I. Pigment Red
57:1, C.I. Pigment Red 81, C.I. Pigment Red 122, and C.I. Pigment Red 5;
red dyes, such as C.I. Solvent Red 49, C.I. Solvent Red 52, C.I Solvent
Red 58, and C.I. Solvent Red 8; blue pigments and dyes of copper
phthalocyanine, such as C.I. Pigment Blue 15:3, and derivatives thereof;
green pigments, such as C.I. Pigment Green 7 and C.I. Pigment Green 36
(Phthalocyanine Green). These pigments or dyes may be used alone or in
combination. These pigments or dyes are preferably added in an amount of
from about 1 to 15 parts by weight, based on 100 parts by weight of the
binder resin.
The charge control agents usable in the present invention are one or more
of the positive charge control agents which are conventionally used in
electrophotography. Examples thereof include nigrosine dyes such as
"BONTRON N-01" (manufactured by Orient Chemical), "BONTRON N-07"
(manufactured by Orient Chemical), "BONTRON N-09" (manufactured by Orient
Chemical), and "BONTRON N-04" (manufactured by Orient Chemical);
triphenylmethane derivatives, such as "COPY BLUE PR" (manufactured by
Hoechst); quaternary ammonium salt compounds such as "TP-415"
(manufactured by Hodogaya Chemical), "COPY CHARGE PSY" (manufactured by
Hoechst), "BONTRON P-51" (manufactured by Orient Chemical),
cetyltrimethylammonium bromide; polyamine resins such as "BONTRON P-52"
(manufactured by Orient Chemical), with a preference given to BONTRON
N-07.
The above charge control agents may be added the binder resin in an amount
of 0.1 to 8.0 parts by weight, preferably 0.2 to 5.0 parts by weight,
based on 100 parts by weight of the binder resin.
The offset inhibitors which are optionally added in the present invention
include waxes, such as polyolefins.
The positively chargeable toners for a nonmagnetic one-component developing
method can be prepared by any of conventionally known methods without
particular limitation. For instance, examples thereof include the methods
comprising kneading, powdering, and classifying; and the methods for
directly preparing the toners comprising suspending in an aqueous
dispersing medium, a polymerizable composition comprising polymerizable
monomers, polymerization initiators, colorants, and charge control agents,
and polymerizing the monomeric components. The resulting untreated toners
are subjected to a surface-treatment by externally adding the fine
polytetrafluoroethylene particles by the methods described above. In the
above methods, property improvers, such as free flow agents and
cleanability improvers, may be optionally added.
Examples of the free flow agents include silica, alumina, titanium oxide,
barium titanate, magnesium titanate, calcium titanate, strontium titanate,
zinc oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth,
chromium oxide, cerium oxide, red oxide, antimony trioxide, magnesium
oxide, zirconium oxide, barium sulfate, barium carbonate, calcium
carbonate, silicon carbide, and silicon nitride, with a preference given
to finely powdered silica.
The finely powdered silica is a fine powder having Si-O-Si linkages, which
may be prepared by either the dry process or the wet process. The finely
powdered silica may be not only anhydrous silicon dioxide but also any one
of aluminum silicate, sodium silicate, potassium silicate, magnesium
silicate and zinc silicate, with a preference given to those containing
not less than 85% by weight of SiO.sub.2. Further, finely powdered silica
surface-treated with a silane coupling agent, a titanium coupling agent,
silicone oil, and silicone oil having amine in the side chain thereof can
be used.
The cleanability improvers include fine powders of metal salts of higher
fatty acids typically exemplified by zinc stearate.
The positively chargeable toner of the present invention is usable in a
nonmagnetic one-component developing method. In particular, the effects of
the present invention become more remarkably noted by utilizing the
nonmagnetic one-component developing methods using positively charged
organic photoconductors.
The positively chargeable toner of the present invention gives little
background on the photoconductors even when the organic photoconductors
are used in a case of utilizing nonmagnetic one-component developing
methods, thereby increasing the durability of the photoconductor.
Therefore, by using the positively chargeable toner of the present
invention, excellent image quality, fixing ability, and durability can be
achieved in the formed images.
EXAMPLES
The present invention is hereinafter described in more detail by means of
the following resin production example, examples, and comparative
examples, without intending to limit the scope of the present invention
thereto. Here, the glass transition temperature (Tg) of the resin was
measured by a differential scanning calorimeter under the following
conditions.
Specifically, the glass transition temperature refers to the temperature of
an intersection of the extension of the baseline of not more than the
glass transition temperature and the tangential line showing the maximum
inclination between the kickoff of the peak and the top thereof as
determined with a sample using a differential scanning calorimeter ("DSC
Model 210," manufactured by Seiko Instruments, Inc.), at a heating rate of
10.degree. C./min. The sample is treated before measurement using the DSC
by raising its temperature 100.degree. C., keeping at 100.degree. C. for 3
minutes, and cooling the hot sample at a cooling rate of 10.degree.
C./min. to room temperature. The acid value was measured by the method
according to JIS K0070.
Preparation Example 1 (Preparation of Binder Resin A)
Three-thousand and five-hundred grams of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, 50 g of
isododecenylsuccinic acid anhydride, 1110 g of fumaric acid, 2.5 g of
hydroquinone, and 5 g of dibutyltin oxide were placed in a ten-liter
four-neck glass flask equipped with a thermometer, a stainless steel
stirring rod, a reflux condenser, and a nitrogen inlet tube. The contents
were allowed to react with one another at 210.degree. C. in a mantle
heater in a nitrogen gas stream while stirring the contents.
The degree of polymerization was monitored from a softening point measured
by the method according to ASTM E 28-67, and the reaction was terminated
when the softening point reached 115.degree. C.
The resulting resin had a glass transition temperature (Tg) with a single
peak at 60.degree. C. Also, the resin had an acid value of 6 KOH mg/g.
This resin is referred to as "Binder Resin A."
Preparation Example 2 (Preparation of Binder Resin B).
Two-thousand six-hundred and thirty grams of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, 1050 g of
polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, 970 g of
terephthalic acid, 335 g of isododecenylsuccinic acid anhydride, 310 g of
trimellitic acid, and 13 g of dibutyltin oxide were placed in a ten-liter
four-neck glass flask equipped with a thermometer, a stainless steel
stirring rod, a reflux condenser, and a nitrogen inlet tube. The contents
were allowed to react with one another at 230.degree. C. in a mantle
heater in a nitrogen gas stream while stirring the contents.
The degree of polymerization was monitored from a softening point measured
by the method according to ASTM E 28-67, and the reaction was terminated
when the softening point reached 149.degree. C.
The resulting resin had a glass transition temperature (Tg) with a single
peak at 62.degree. C. Also, the resin had an acid value of 6 KOH mg/g.
This resin is referred to as "Binder Resin B."
Preparation Example 3 (Preparation of Binder Resin C)
Two-thousand six-hundred and thirty grams of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, 1050 g of
polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, 1015 g of
terephthalic acid, 335 g of isododecenylsuccinic acid anhydride, 310 g of
trimellitic acid, and 13 g of dibutyltin oxide were placed in a ten-liter
four-neck glass flask equipped with a thermometer, a stainless steel
stirring rod, a reflux condenser, and a nitrogen inlet tube. The contents
were allowed to react with one another at 230.degree. C. in a mantle
heater in a nitrogen gas stream while stirring the contents.
The degree of polymerization was monitored from a softening point measured
by the method according to ASTM E 28-67, and the reaction was terminated
when the softening point reached 150.degree. C.
The resulting resin had a glass transition temperature (Tg) with a single
peak at 65.degree. C. Also, the resin had an acid value of 9 KOH mg/g.
This resin is referred to as "Binder Resin C."
Preparation Example 4 (Preparation of Binder Resin D)
Two-thousand six-hundred and thirty grams of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, 1050 g of
polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, 970 g of
terephthalic acid, 480 g of isododecenylsuccinic acid anhydride, 310 g of
trimellitic acid, and 13 g of dibutyltin oxide were placed in a ten-liter
four-neck glass flask equipped with a thermometer, a stainless steel
stirring rod, a reflux condenser, and a nitrogen inlet tube. The contents
were allowed to react with one another at 230.degree. C. in a mantle
heater in a nitrogen gas stream while stirring the contents.
The degree of polymerization was monitored from a softening point measured
by the method according to ASTM E 28-67, and the reaction was terminated
when the softening point reached 145.degree. C.
The resulting resin had a glass transition temperature (Tg) with a single
peak at 60.degree. C. Also, the resin had an acid value of 12 KOH mg/g.
This resin is referred to as "Binder Resin D," which is a comparative
binder resin of the present invention.
Example 1
______________________________________
Binder Resin A 100 parts by weight
Carbon Black "REGAL 330R"
4 parts by weight
(Manufactured by Cabot Corporation)
Nigrosine Dye "BONTRON N-04"
4 parts by weight
(Manufactured by Orient Chemical
Co., Ltd.)
Low-Molecular Weight Polypropylene Wax
2 parts by weight
"MITSUI HIWAX NP-055," manufactured by
Mitsui Petrochemical Industries, Ltd.)
______________________________________
The starting materials in the above proportions were blended well in
advance, and then the mixture was kneaded using a twin-screw extruder
heated at 100.degree. C. The resulting mixture was cooled, and the cooled
product was roughly pulverized, to a size of 2 mm-mesh pass by a
mechanical pulverizer. Thereafter, the roughly pulverized mixture was
finely powdered using a jet mill, and the resulting finely powdered
mixture was classified using an air classifier, to give an untreated toner
having an average particle size of 8.0 .mu.m, the average particle size
being D50 (volume) size distribution measured by a Coulter counter
"MULTISIZER" (manufactured by COULTER Corporation). In the following
examples, the average particle size was measured in the same manner as
above. In Examples and Comparative Examples, the untreated toner means
"toner particle" in the present invention.
To the surface of the untreated toner, 0.3 parts by weight of the fine PTFE
(polyethylenetetrafluoroethylene) particles "KTL-500F" (manufactured by
Kitamura) having an average primary particle size of 0.3 .mu.m and 0.5
parts by weight of 20 nm-alumina subjected to a hydrophobic treatment with
hexamethyldisilazane (BET specific surface area: 100 m.sup.2 /g; "TM-100,"
manufactured by Taimei Kagaku) were externally added. Thereafter, a toner
was prepared by subjecting the untreated toner to a surface treatment by
blending the fine particles together with the untreated toner using a
Henschel mixer.
Here, the amounts of both PTFE and alumina were based on 100 parts by
weight of the untreated toner.
Example 2
______________________________________
Binder Resin B 100 parts by weight
Carbon Black "REGAL 330R"
4 parts by weight
(Manufactured by Cabot Corporation)
Nigrosine Dye "BONTRON N-04"
4 parts by weight
(Manufactured by Orient Chemical
Co., Ltd.)
Low-Molecular Weight Polypropylene Wax
2 parts by weight
"MITSUI HIWAX NP-055," manufactured by
Mitsui Petrochemical Industries, Ltd.)
______________________________________
The starting materials in the above proportions were blended well in
advance, and then the mixture was kneaded using a twin-screw extruder
heated at 100.degree. C. The resulting mixture was cooled, and the cooled
product was roughly pulverized, to a size of 2 mm-mesh pass by a
mechanical pulverizer. Thereafter, the roughly pulverized mixture was
finely powdered using a jet mill, and the resulting finely powdered
mixture was classified using an air classifier, to give an untreated toner
having an average particle size of 8.0 .mu.m, the average particle size
being D50 (volume) of size distribution measured by a Coulter counter.
To the surface of the untreated toner, 0.3 parts by weight of the fine PTFE
particles "KTL-500F" (manufactured by Kitamura) having an average primary
particle size of 0.3 .mu.m and 0.5 parts by weight of 20 nm-alumina
subjected to a hydrophobic treatment with hexamethyldisilazane (BET
specific surface area: 100 m.sup.2 /g; "TM-100," manufactured by Taimei
Kagaku) were externally added. Thereafter, a toner was prepared by
subjecting the untreated toner to a surface treatment by blending the fine
particles together with the untreated toner using a Henschel mixer.
Here, the amounts of both PTFE and alumina were based on 100 parts by
weight of the untreated toner.
Example 3
______________________________________
Binder Resin C 100 parts by weight
Carbon Black "REGAL 330R"
4 parts by weight
(Manufactured by Cabot Corporation)
Nigrosine Dye "BONTRON N-04"
4 parts by weight
(Manufactured by Orient Chemical
Co., Ltd.)
Low-Molecular Weight Polypropylene Wax
2 parts by weight
"MITSUI HIWAX NP-055," manufactured by
Mitsui Petrochemical Industries, Ltd.)
______________________________________
The starting materials in the above proportions were blended well in
advance, and then the mixture was kneaded using a twin-screw extruder
heated at 100.degree. C. The resulting mixture was cooled, and the cooled
product was roughly pulverized, to a size of 2 mm-mesh pass by a
mechanical pulverizer. Thereafter, the roughly pulverized mixture was
finely powdered using a jet mill, and the resulting finely powdered
mixture was classified using an air classifier, to give an untreated toner
having an average particle size of 8.0 .mu.m, the average particle size
being D50 (volume) of size distribution measured by a Coulter counter.
To the surface of the untreated toner, 0.3 parts by weight of the fine PTFE
particles "KTL-500F" (manufactured by Kitamura) having an average primary
particle size of 0.3 .mu.m and 0.5 parts by weight of 20 nm-alumina
subjected to a hydrophobic treatment with hexamethyldisilazane (BET
specific surface area: 100 m.sup.2 /g; "TM-100," manufactured by Daimei
Kagaku) were externally added. Thereafter, a toner was prepared by
subjecting the untreated toner to a surface treatment by blending the fine
particles together with the untreated toner using a Henschel mixer.
Here, the amounts of both PTFE and alumina were based on 100 parts by
weight of the untreated toner.
Comparative Example 1
______________________________________
Binder Resin D 100 parts by weight
Carbon Black "REGAL 330R"
4 parts by weight
(Manufactured by Cabot Corporation)
Nigrosine Dye "BONTRON N-04"
4 parts by weight
(Manufactured by Orient Chemical
Co., Ltd.)
Low-Molecular Weight Polypropylene Wax
2 parts by weight
"MITSUI HIWAX NP-055," manufactured by
Mitsui Petrochemical Industries, Ltd.)
______________________________________
The starting materials in the above proportions were blended well in
advance, and then the mixture was kneaded using a twin-screw extruder
heated at 100.degree. C. The resulting mixture was cooled, and the cooled
product was roughly pulverized, to a size of 2 mm-mesh pass by a
mechanical pulverizer. Thereafter, the roughly pulverized mixture was
finely powdered using a jet mill, and the resulting finely powdered
mixture was classified using an air classifier, to give an untreated toner
having an average particle size of 8.0 .mu.m, the average particle size
being D50 (volume) of size distribution measured by a Coulter counter.
To the surface of the untreated toner, 0.3 parts by weight of the fine PTFE
particles "KTL-500F" (manufactured by Kitamura) having an average primary
particle size of 0.3 .mu.m and 0.5 parts by weight of 20 nm-alumina
subjected to a hydrophobic treatment with hexamethyldisilazane (BET
specific surface area: 100 m.sup.2 /g; "TM-100," manufactured by Taimei
Kagaku) were externally added. Thereafter, a toner was prepared by
subjecting the untreated toner to a surface treatment by blending the fine
particles together with the untreated toner using a Henschel mixer.
Here, the amounts of both PTFE and alumina were based on 100 parts by
weight of the untreated toner.
Comparative Example 2
______________________________________
Binder Resin B 100 parts by weight
Carbon Black "REGAL 330R"
4 parts by weight
(Manufactured by Cabot Corporation)
Nigrosine Dye "BONTRON N-04"
4 parts by weight
(Manufactured by Orient Chemical
Co., Ltd.)
Low-Molecular Weight Polypropylene Wax
2 parts by weight
"MITSUI HIWAX NP-055," manufactured by
Mitsui Petrochemical Industries, Ltd.)
______________________________________
The starting materials in the above proportions were blended well in
advance, and then the mixture was kneaded using a twin-screw extruder
heated at 100.degree. C. The resulting mixture was cooled, and the cooled
product was roughly pulverized, to a size of 2 mm-mesh pass by a
mechanical pulverizer. Thereafter, the roughly pulverized mixture was
finely powdered using a jet mill, and the resulting finely powdered
mixture was classified using an air classifier, to give an untreated toner
having an average particle size of 8.0 .mu.m, the average particle size
being D50 (volume) of size distribution measured by a Coulter counter.
To the surface of the untreated toner, 0.5 parts by weight of 20 nm-alumina
subjected to a hydrophobic treatment with hexamethyldisilazane (BET
specific surface area: 100 m.sup.2 /g; "TM-100," manufactured by Taimei
Kagaku) were externally added. Thereafter, a toner was prepared by
subjecting the untreated toner to a surface treatment by blending the fine
particles together with the untreated toner using a Henschel mixer.
Here, the amounts of the alumina were based on 100 parts by weight of the
untreated toner.
Comparative Example 3
______________________________________
Styrene/n-Butylmethacrylate
100 parts by weight
(weight ratio: 65/35; weight-average
molecular weight: 67000; Tg: 64.degree. C.)
Carbon Black "REGAL 330R"
4 parts by weight
(Manufactured by Cabot Corporation)
Nigrosine Dye "BONTRON N-04"
4 parts by weight
(Manufactured by Orient Chemical
Co., Ltd.)
Low-Molecular Weight Polypropylene Wax
2 parts by weight
"MITSUI HIWAX NP-055," manufactured by
Mitsui Petrochemical Industries, Ltd.)
______________________________________
The starting materials in the above proportions were blended well in
advance, and then the mixture was kneaded using a twin-screw extruder
heated at 100.degree. C. The resulting mixture was cooled, and the cooled
product was roughly pulverized, to a size of 2 mm-mesh pass by a
mechanical pulverizer. Thereafter, the roughly pulverized mixture was
finely powdered using a jet mill, and the resulting finely powdered
mixture was classified using an air classifier, to give an untreated toner
having an average particle size of 8.0 .mu.m, the average particle size
being D50 (volume) of size distribution measured by a Coulter counter.
To the surface of the untreated toner, 0.3 parts by weight of the fine PTFE
particles "KTL-500F" (manufactured by Kitamura) having an average primary
particle size of 0.3 .mu.m and 0.5 parts by weight of 20 nm-alumina
subjected to a hydrophobic treatment with hexamethyldisilazane (BET
specific surface area: 100 m.sup.2 /g; "TM-100," manufactured by Taimei
Kagaku) were externally added. Thereafter, a toner was prepared by
subjecting the untreated toner to a surface treatment by blending the fine
particles together with the untreated toner using a Henschel mixer.
Here, the amounts of both PTFE and alumina were based on 100 parts by
weight of the untreated toner.
Comparative Example 4
Similar procedures as in Example 2 were carried out except for externally
adding fine polyvinylidene fluoride particles "KYNAR-461" (manufactured by
PENNWALT) having an average primary particle size of 0.3 .mu.m to the
untreated toner in place of the fine PTFE particles "KTL-500F" having an
average primary particle size of 0.3 .mu.m, to prepare a toner.
Comparative Example 5
Similar procedures as in Example 2 were carried out except for externally
adding fine styrene-methyl methacrylate copolymer particles "NK-32"
(manufactured by Nippon Paint Co., Ltd.) having an average primary
particle size of 0.080 .mu.m to the untreated toner in place of the fine
PTFE particles "KTL-500F" having an average primary particle size of 0.3
.mu.m, to prepare a toner.
Test Example
Each of the toners prepared above as developers was loaded in a modified
plain paper facsimile "TF-5500" (manufactured by Toshiba Corporation)
whose photoconductor was changed to the following positively charged
organic photoconductor (single-layered OPC), a surface voltage was +800 V,
a developing bias voltage was +300 V, a supplying bias voltage was +400 V,
and a transfer roller voltage was -1100 V, to evaluate the fixing ability
of the toner and durability of the developer for 20000-sheet intermittent
printing according to the evaluation standards given below.
The positively charged organic photoconductor used herein was a
single-layered OPC wherein a fluorenone bisazo pigment and a
tetraphenyldiamine (TPD) compound having the following formulas were
applied on a substrate. Specifically, 5 parts by weight of the bisazo
pigment and 100 parts by weight of the TPD were uniformly dispersed in 100
parts by weight of a polycarbonate resin, and the resulting mixture was
applied on an aluminum substrate by a dip coating method so as to give a
thickness, on a dry basis, of about 30 .mu.m.
##STR3##
(a) Image Quality:
Evaluated by gross examination, background on photoconductor, toner
scattering, uneven formed images.
.circleincircle.: Excellent;
.smallcircle.: Good;
.DELTA.: Practically usable; and
x: Not usable for practical purposes.
(b) Fixing Ability:
Evaluated by the lowest and highest non-offset values (non-offset region),
and by the fastness test of the fixed images. Here, the practical range of
the non-offset region was about 50.degree. C. or more.
.smallcircle.: Good;
.DELTA.: Practically usable; and
x: Not usable for practical purposes.
(c) Durability:
Evaluated by testing the image quality of item (a) after a 20000-sheet
intermittent printing with papers containing 5% dark portions, and also
evaluated by gross examination the extent of deterioration of the
photoconductor, the developer roller, and the developing blade.
.smallcircle.: Good;
.DELTA.: Practically usable; and
X: Not usable for practical purposes.
The results are shown in Table 1.
TABLE 1
______________________________________
Image Fixing
Quality Ability Durability
______________________________________
Examples
1 .circleincircle.
O O
2 O O O
3 O O O
Comparative Examples
1 .DELTA. O .DELTA.
2 X O X
3 O X X
4 O O X
5 .DELTA. .DELTA. X
______________________________________
As is shown in Table 1, in the cases of Example 1 to 3 where the positively
chargeable toners of the present invention were used, the resulting toners
were all good in image quality, the fixing ability, and the durability. In
particular, in the case of Example 1 where the polyester used as a binder
resin is prepared by condensation polymerization of the polycarboxylic
acid component other than the aromatic polycarboxylic acid and the
polyhydric alcohol, the resulting toner had remarkably excellent image
quality.
By contrast, in the case of Comparative Example 2 where no fine PTFE
particles were added for surface treatment, the resulting toner had
notably poor image quality and durability. In the case of Comparative
Example 4 where the fine polyvinylidene fluoride particles were added for
surface treatment, the resulting toner had notably poor durability. In the
case of Comparative. Example 5 where the fine styrene-methyl methacrylate
copolymer particles were used for surface treatment, the resulting toner
had slightly poor image quality and fixing ability, and also notably poor
durability. In the case of Comparative Example 1 where an acid value
exceeds 10 mg KOH/g, the resulting toner had slightly poor image quality
and durability. In the case of Comparative Example 3 where a
styrene-n-butyl methacrylate copolymer was used, the resulting toner had
poor fixing ability and durability.
Here, excellent image quality can be obtained in the cases where the
positively chargeable toners of the present invention were used primarily
because the triboelectric charging of the toners can be well performed.
The present invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be regarded as
a departure from the spirit and scope of the invention, and all such
modifications as would be obvious to one skilled in the art are intended
to be included within the scope of the following claims.
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